Abstract: The disclosed invention is an inexpensive, simple and reusable device to aid in setting the spark plug timing of an internal combustion engine by allowing one person to detect a piston's top dead center. In function, the detector is sealably inserted into a spark plug port and is forcibly expelled by the pressure maximum that occurs at top dead center. The detector's expulsion is accompanied by a "pop" sound similar to when a champagne cork is expelled from its bottle, and which can be remotely perceived by the user.